Volatile organic compounds, or VOCs, are substances that contain carbon and evaporate (becomes a vapor) or “off-gases” at room temperature. VOCs are human-made and do not occur naturally in drinking water. Hundreds of VOCs have been made for a variety of products—such as gasoline, dry cleaning solvents, and degreasing agents. When these products are improperly stored or disposed of, or when a spill occurs, VOCs can contaminate groundwater and drinking water supplies.
Although many VOCs found in drinking water are due to contamination, others may be formed when drinking water is treated with chlorine to disinfect it. The chlorine reacts with organic materials found in water and forms certain VOCs known as chlorination byproducts. Learn more about disinfection byproducts.
The Vermont Department of Environmental Conservation regulates VOCs in public water systems.
If you suspect that your private drinking water is contaminated by VOCs, stop drinking the water and call the Health Department at: 802-863-7220 or 800-439-8550 (toll free in Vermont).
Drinking water that contains VOCs can increase your risk for a variety of health problems. Some VOCs have been proven to cause cancer after prolonged exposure, while others are considered possible cancer risks. VOCs can also cause other health problems.
Reducing the amount of chlorine added to your water, or using an activated carbon filter, can sometimes reduce VOCs formed during chlorination. If the VOCs are not caused by chlorination, it’s important to find the source. Additional testing may be needed to determine the level of contamination. There are two ways to remove VOCs from drinking water: activated carbon/charcoal and reverse osmosis.
Water passes through an activated carbon filter. The VOCs bond to active sites in the carbon passages and are removed from the water. Over time, the active sites fill up and the filter is no longer effective. If the filter continues to be used at this point, the VOCs may be released back into the filtered water. Be sure to follow the maintenance schedule recommended by the manufacturer because disease-causing bacteria can build up in the filter.
A thin membrane allows pressurized water to pass through while holding back any pollutants to be drained off. This process uses three to 10 gallons of untreated water to make one gallon of drinking water. Reverse osmosis can remove many VOCs but not all chlorination byproducts. Chlorine can damage some reverse osmosis membranes, so pretreatment may be needed.